In a normal universe, snubbing nine out of 10 voters wouldn’t be a path to victory. But New York is no normal universe. It’s a place where an endorsement from the teachers union trumps the popular will — which explains why three of the five top Democratic candidates for mayor are running away from charter schools.

Their latest run was a real profile in courage. It came Tuesday at a forum sponsored by Families for Excellent Schools and other charter advocates. Ex-city Comptroller Bill Thompson and Public Advocate Bill de Blasio had agreed to attend. But organizers say the two backed out at the last minute after learning they’d have to own up to their anti-charter positions before the crowd.

There’s no question New Yorkers want charters. In a new Zogby poll commissioned by the Manhattan Institute, 86 percent of likely city voters said parents should have more options for their kids — of which charters are the most compelling example. At one charter school recently, 12,500 applicants applied for 1,400 slots.

But there’s also no question that the teachers union — which is set to announce its endorsement any day — finds charters anathema. So anyone hoping for that endorsement will be more than willing to give the 86 percent the shaft, as John Liu did openly (to boos) at Tuesday’s forum, and as de Blasio and Thompson did by fleeing from it.

True, ex-Rep. Anthony Weiner and City Council Speaker Chris Quinn did appear at the event and even expressed support for charters and other options for kids.

But we’re still looking for the candidate who will go beyond polite defenses of existing charters to make the debate about how to aggressively expand them. We know it’s not easy to stand up to the teachers union in this town. But the 86 percent of New Yorkers who agree that parents need more choice suggests the opportunity is there for a candidate with the sense to seize it.